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Hot-Water Therapy for Geranium Rust Control. Douglas J. Phillips, Plant Pathologist, ARS, USDA, 2021 South Peach Avenue, Fresno, California 93727; Arthur H. McCain, Extension Plant Pathologist, Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 63:273-275. Accepted for publication 30 August 1972. DOI: 10.1094/Phyto-63-273.

Rust incited by Puccinia pelargonii-zonalis did not develop on infected geranium cuttings, Pelargonium hortorum (× P. zonale), after they were dipped for 90 sec in water at 50 or 52 C, or were held 24 or 48 hr in water-saturated air at 38 C. The hot-water treatment permitted germination of some urediospores, particularly those taken from poorly growing plants. Hot water damaged small expanding leaves, but did not retard subsequent plant growth.